An Investigation on Effect of Parasitic Resistances on Grid Connected PV System

摘要

This paper investigates the variation of eigenvalues and dynamic properties of different control loops in a grid connected PV inverter (GCPVI) with variation in dynamic resistance of PV source and internal resistance of associated passive components. Because of the nonlinearities of GCPVI, small signal modeling (SSM) is necessary to investigate the dynamics of GCPVI. Dynamics of the GCPVI depend upon the nature of the input source as well as passive components of the system, i.e., interfacing filter and DC-link capacitor. The dynamic resistance of the PV input source is varied with its operating point. Also, internal resistance of passive components in a GCPVI varies with time. By pursuing a detailed study on the frequency responses and eigenvalue analysis, it is observed that the GCPVI dynamics vary significantly with the aforesaid perturbation in different resistances. This further deteriorates the maximum power point tracking (MPPT) efficiency. Due to the increase of internal resistance of DC-link capacitor from 0 to 1.5 Ω the MPPT efficiency decreases from 99.97 to 99.4%. This analysis will help the designer in ensuring the satisfactory performance of GCPVI in the event of perturbation owing to the aging effect in the passive components.